Magnesium Oxychloride Cement

ABSTRACT

Magnesium oxychloride cement is formed by mixing a magnesium chloride (MgCl 2 ) brine solution with a magnesium oxide (MgO) composition in a selected stoichiometric ratio of MgCl 2 , MgO, and H 2 O that forms the 5 phase magnesium oxychloride cement composition. Although Sorel cements formed from the mixture of MgCl 2 , MgO can form a variety of compounds, the inventive systems and methods provide for controlling the cement kinetics to form the five phase magnesium oxychloride cement composition and results in an improved and stable cement composition. Various fillers can be optionally added to form preferred cement materials for uses as diverse such as road stripping, fire-proofing, fire barriers, cement repair, and mortar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application that claims the benefit ofU.S. Non-Provisional patent application Ser. No. 11/936,717, entitled“Magnesium Oxychloride Cement” and filed on Nov. 7, 2007 that, in turn,claims the benefit of U.S. Provisional Application No. 60/866,184entitled “Magnesium Oxychloride Cement” and filed on Nov. 16, 2006, eachof which is incorporated herein by this reference for all purposes.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to the fields of cement compositions andproducts. More particularly, the present invention relates to improvedmagnesium oxychloride cement compositions.

2. The Relevant Technology

Cement and cementitious products affect everyone, from the roads wedrive on, to the buildings we work in, to the homes we live in. Earlyprinciples and applications of cement and cement products were knownanciently. The Romans, for example, developed cements and cementproducts to a high degree of sophistication. Despite centuries ofknowledge concerning cements and cement products and despite countlessvariations of cement compositions, problems still arise while usingcements which heretofore have not been adequately solved.

One of the most important uses of cement compositions is in concrete. Asused herein, the term “concrete” is broadly defined as a hard strongbuilding material made by mixing an aqueous solution-cementitious powdermixture with a mineral aggregate, often sand and gravel. The cement actsas a glue to bind the aggregate particles together. The setting time andphysical properties of concrete vary depending on the cement compositionand upon the choice of aggregates.

Concrete is commonly used to construct driveways, sidewalks, floors, androads (hereinafter referred to generically as “road surfaces”). Concreteroad surfaces are usually constructed of Portland cement as a mixture ofcalcium oxide and water with gravel as an aggregate. Although Portlandcement is the industry standard, it is generally slow setting andrequires a substantial cure time to reach an acceptable strength. Infact, it has been estimated that Portland cement does not reach fullstrength for about 100 years.

Sorel cement is another common type of cement. It is a hydraulic cementmixture of magnesium oxide (burnt magnesia) with magnesium chloridetogether with aggregate materials like sand or crushed stone.Conventional Sorel cement has a poor resistance to water, making itunsuitable for many applications, but is widely used for use ingrindstones, tiles, artificial stone (cast stone), cast floors, and evenartificial ivory (e.g. for billiard-balls). Magnesia cement floors arecredited a high resistance to wear.

Sorel cement is produced by mixing a MgCl₂ brine solution with MgOpowder. Conventional Sorel cement has a weight ratio 2.5-3.5 parts MgOto one part MgCl₂. There is considerable controversy as to what chemicalreaction is responsible for the setting reaction of Sorel cement. In theliterature, there are several setting reactions presented. The two mostprominent are the formation of a 5-phase hydrated magnesium oxychlorideproduct (5Mg(OH)₂.MgCl₂.8H₂O) and a 3-phase hydrated magnesiumoxychloride product (3Mg(OH)₂.MgCl₂.8H₂O), each formed according toEquations 1 and 2 below, respectively.

5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O  Equation 1

3MgO+MgCl₂+11H₂O→3Mg(OH)₂.MgCl₂.8H₂O  Equation 2

Other potential setting reactions discussed include the formation of2-phase (2Mg(OH)₂.MgCl₂.4H₂O), 9-phase (9Mg(OH)₂.MgCl₂.5H₂O), Mg(OH)₂and MgCl₂.6H₂O. In addition to the confusion over the setting reaction,there is a lack of knowledge of the kinetics of the setting reaction andthe resulting strength of cements made under different conditions.Further details regarding Sorel cements can be found in U.S. Pat. Nos.5,004,505 and 5,110,361 to Russell I. Alley and George E. Caine, both ofwhich patents are incorporated herein by reference in their entireties.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to improved Sorel cement (magnesiumoxychloride) compositions and products. The inventive cementcompositions can be used for a variety of purposes, from conventionaluse in repairing damaged concrete surfaces and coating substrates with astucco-like surface to fireproofing underlying materials, forming fireproof layers and fire barriers such as fire barrier doors, and providingdurable traffic paint.

The present invention represents an improvement on conventional Sorelcement systems. As previously noted, the basic Sorel system includescalcined magnesia (MgO, also known as magnesium oxide) mixed with anaqueous solution of magnesium chloride (MgCl₂). In the presentinvention, the ratio of magnesium oxide to magnesium chloride in thecement composition is carefully controlled to ensure that the properreaction pathway occurs so that durable and strong Sorel cement results.

By way of example, the use of brine from the Great Salt Lake as a sourceof magnesium chloride results in a cement composition which is not onlyless expensive than cement compositions made from pure magnesiumchloride solutions, but also substantially stronger.

Accordingly, a first example embodiment of the invention is a method forforming a cementitious composition. The method generally includes:providing a first volume of a magnesium chloride (MgCl₂) brine solution;providing a second volume of a magnesium oxide (MgO) composition, thesecond volume and the first volume having a weight ratio that is basedupon their respective concentrations and is selected to providesufficiently stoichiometric ratios of MgCl₂, MgO, and H₂O to preferablyform a magnesium oxychloride cement composition according to the 5 phasereaction: 5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O; and mixing the firstvolume with the second volume to form the magnesium oxychloride cementmixture. The magnesium chloride brine solution preferably has a specificgravity in the range from about 28° Baume to about 34° Baume, morepreferably at least about 30° Baume. The brine solution is preferablyGreat Salt Lake brine having impurities ranging from about 1% to about5% as illustrated by example elsewhere herein. The magnesium oxidecomposition also contains salt or mineral impurities other thanmagnesium oxide, the total amount of the impurities being in the rangefrom about 5% to about 20% of the magnesium oxide composition. Themethod also optionally includes adding one or more filler materials withthe magnesium oxychloride cement composition mixture.

Another example embodiment is a cementitious material formed of amagnesium oxychloride cement comprising at least about 80% of the 5phase compound 5Mg(OH)₂.MgCl₂.8H₂O after 24 hours, more preferably atleast about 90% of the 5 phase compound after 24 hours, still morepreferably at least about 98% of the 5 phase compound after 24 hours.The cementitious material can be advantageously used in a number ofapplications as disclosed herein, for example as a fire proof coating.In other words, embodiments of the invention minimize the amount ofpoorly water resistant MgCl₂.6H₂O formed from a 3 phase reaction.

In another example embodiment of the invention, a cementitious materialincludes: a magnesium oxychloride cement produced by combiningingredients in a selected ratio. The ingredients include: a magnesiumchloride brine solution at a first weight percent of the magnesiumoxychloride cement, the brine solution having a specific gravity in therange of from about 27° Baume to about 34° Baume, a magnesium oxidecomposition at a second weight percent of the Sorel cement, and one ormore filler materials mixed with the magnesium oxychloride cement. Theratio of the first weight percent to the second weight percent isselected to provide substantially stoichiometric ratios of MgCl₂ and H₂Oto MgO to form a magnesium oxychloride cement composition according tothe 5 phase reaction:

5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O.

Another example embodiment is a fire barrier door formed of a door framehaving front and back surfaces and a cement core between the front andback surfaces, the cement core comprising magnesium oxychloride cementcomprising at least about 80% of the 5 phase compound5Mg(OH)₂.MgCl₂.8H₂O and a lightweight filler.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to improved magnesium oxychloridecement compositions and products formed therefrom having improvedstrength and durability. The improved cements are formed of improvedmagnesium oxychloride (also known as Sorel cement) compositions andproducts. The disclosed products and methods represent an improvement onconventional Sorel cement systems, which include calcined magnesia (MgO,also known as magnesium oxide) mixed with an aqueous solution ofmagnesium chloride (MgCl₂). In the present invention, the ratio ofmagnesium oxide to magnesium chloride in the cement composition iscarefully controlled to ensure that the proper reaction pathway occursso that durable and strong cement results.

The following disclosure includes discussions on compositions, methods,example embodiments of the invention, and finally a few examples. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. It will beobvious, however, to one skilled in the art that the present inventionmay be practiced without these specific details. In other instances,well-known aspects of cementitious compositions and constructiontechniques have not been described in particular detail in order toavoid unnecessarily obscuring the present invention.

It will be appreciated by those skilled in the art, in view of thedisclosure herein, that the present invention provides cementcompositions which possess a high structural strength, and yet have ahigh bonding strength to common substrates. The cement compositions setrelatively fast, but do not set so fast as to prevent adequate “working”of the compositions to form the desired end product. The presentinvention also provides cement compositions which do not shrink uponsetting in order that a good bond can be formed with the adjacentsurface, such as when used to repair deteriorating concrete roadsurfaces. The cement compositions are also resistant, for example, toheat and flame, weather exposure, ultraviolet rays, and deicing salts.

I. Compositions

The inventive cement compositions are generally formed from magnesiumoxychloride in an aqueous solution, magnesium oxide, and optionally oneor more filler materials, each as discussed below.

A. Magnesium Chloride

Magnesium Chloride (MgCl₂) is preferably provided in solution with thewater necessary for the cement formation when mixed with MgO. Accordingto the invention it has been found that the magnesium chloride solutionshould have a specific gravity in the range of from about 28° to about34°, more preferably at least about 30°. Slight disparities betweenoptimum values of specific gravity and proportions of ingredients may bepermissible. Nevertheless, it is preferable that the specific gravity ofthe gauging solution be maintained within a suitable range to ensure theproper stoichiometric ratio is used to form the preferred five phasereaction product.

When the specific gravity of the solution exceeds the suitable range(that is, the solution has a very high degree Baume) the excessmagnesium chloride will tend to absorb the moisture from the atmospherecausing the surface of the cement to expand slightly or otherwise becomeirregular. Similarly, if the specific gravity of the magnesium chloridesolution is below the suitable range, then there will either beunreacted magnesium oxide present which will tend to combine with waterin the solution to form free magnesium hydroxide or there will be excesswater which must evaporate, slowing the curing time of the cement.Magnesium hydroxide forms an impervious surface layer on the magnesiumoxide particles preventing further five phase reaction. Therefore, if anexcessive amount of magnesium hydroxide is present, fissures and cementweakening tend to occur rendering the quality of the concreteunacceptable.

A particularly preferred source of MgCl₂ is a concentrated brinesolution from the Great Salt Lake. The Great Salt Lake brine not only issignificantly less expensive than known magnesium chloride solutionsources, but also results in a cement composition possessingunexpectedly higher strength. Although it is not intended to limit thepresent invention to any specific theory of action or mechanism, it isbelieved that existence of salts and mineral elements other thanmagnesium chloride in the brine solution synergistically react with themagnesium oxide producing the higher strength cement composition. Table1 illustrates a typical composition of Great Salt Lake brine.

TABLE 1 GSL Brine Component Weight Percent MgCl₂ 30.00 to 34.00% Sulfate(SO₄ ⁻²) 0.0 to 3.5% Potassium (K) 0.0 to 0.7% Sodium (Na) 0.0 to 0.7%Water Balance

B. Magnesium Oxide

Magnesium oxide (MgO) can be provided in any of the various compositionsconventionally used to for magnesium oxychloride cements, depending onthe particular application. For example, a pure analytical reagent gradeMgO can be obtained with a purity of 99.999%. More generally, a veryhighly reactive technical grade MgO composition of at least 98% finelysized high purity MgO can be used in chemical process applications wherea rapid reaction rate is necessary. Magnesium oxide of this purity isnot necessary and may not be financially preferable for manyapplications, however. More preferably, an industrial grade product canbe obtained. For example, an industrial grade MgO composition with amakeup as identified in Table 2 below can be used.

TABLE 2 Example Industrial MgO Composition Component Weight Percent MgO85.6% CaO 2.7% SiO₂ 2.1% LOI (H₂O) 4.5% Fe₂O₃ 0.6% Al₂O₃ 0.5% SO₃ 4.0%There may also be other trace metals in this material as it is acalcined natural mineral. It is generally preferred that the used MgOcomposition have a weight percent of MgO of at least 80%, although thisis not necessary provided that that the actual weight percent of MgO inthe MgO composition is accounted for in determining the proper ratio ofMgO to MgCl₂ and H₂O to be mixed to achieve desired stoichiometricratios.

C. Fillers

The choice of fillers added to magnesium oxychloride cement determinesthe suitable uses for the resulting product. As used herein, the term“filler” includes within its meaning all materials that are not themagnesium oxychloride cement or its precursors, including for example“aggregates,” which are inert materials that add a desired mechanicalproperty, and other materials such as tints. In some cases no filler isnecessary where the cement can be applied directly, for example as afireproof coating. In others examples uses, however, the filler can adda valuable strength or volume to the cement. For example, very lightweight aggregates such as expanded polystyrene beads, perlite, pumice,volcanic ash, vermiculite, zircon sands, high alumina sands, etc. aresuitable for light-weight insulation-type uses, whereas very denseaggregates such as silica sands are suitable for concrete surface repairuses. The magnesium oxychloride cement compositions within the scope ofthe present invention may be used with both organic and inorganic(mineral) aggregates, including common soil. Examples of organic fillersinclude wood flour, wood chips, and saw dust. Tints such as yellowpigments and titanium dioxide (white) can be used to effect a desiredcolor as well.

Common mineral aggregates can be used and are graded depending upon thesize of the aggregate. The grading is typically a number correspondingto the number of divisions or meshes per inch of a large screen. Thewell known Tyler Mesh scale can be used. Generally, in grading themineral aggregates, a number is assigned to the size of aggregate whichwill pass through the numbered mesh screen, but not the next smallersized screen.

Specific sizes of mineral aggregate referred to in this specificationare intended to be purely exemplary and should not be viewed as alimitation to the precise size mentioned. For example, a reference to #8silica sand is intended to include those sizes substantially the same as#8 silica sand such as those aggregates having size in the range fromabout #6 to about #10. Similarly, specific size ranges referred to inthis specification such as silica sand having a range from about #8 toabout #70 may include #8, #16, #30, #70, or any other standard gradationtherebetween. A non limiting set of examples of aggregate materials arelisted in Table 3 below.

TABLE 3 Example Filler Characteristics Bulk Density Material (gm/mL)Void Fraction Sand #1 1.383 0.4267 Sand #2 1.400 0.5475 LightweightVolcanic 0.383 0.4750 Lightweight Volcanic Ash #1 0.600 0.5667Lightweight Volcanic Ash #2 0.600 0.4700 Expanded Shale 0.875 0.4538

II. Methods

As previously noted, conventional Sorel cements are formed by mixing MgOand MgCl₂. It has been found that a particular refinement of the methodprovides for an improved cement product, which has been determined to bethe five phase reaction product. Generally, the preferred methodincludes first providing a magnesium chloride (MgCl₂) brine solution anda dry magnesium oxide (MgO) composition in a selected ratio, for examplea weight ratio. This ratio is based upon their respective concentrationsand is adjusted to provide sufficiently stoichiometric ratios of MgCl₂,MgO, and H₂O to preferably form a magnesium oxychloride cementcomposition according to the 5 phase reaction:

MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O

Depending upon the desired quality of product in terms of the percentphase product that is formed and the MgCl₂ and MgO source, and assuminga brine solution having a magnesium chloride a specific gravity in therange of from about 28° to about 34°, this ratio may be as broad as fromabout 1.1:1 to about 1.9:1 by weight, but is more preferably from about1.3:1 to about 1.7:1, and still more preferably is about 1.46:1. Forease of use in industry, the 1.46:1 ratio can be expressed as about onegallon of GSL brine to about 7.5 pounds of an approximately 85% MgOcomposition.

After the MgCl₂ and MgO are provided, they are preferably mixedthoroughly in the appropriate ratio without any fillers for a period ofpreferably at least about 1 minute, more preferably from about fiveminutes to about seven minutes. One or more filler materials areoptionally then admixed before the mixed MgCl₂ and MgO finalize setting.Thorough mixing of the magnesium oxychloride cement compositions withinthe scope of the present invention is important to consistently obtain acomplete chemical reaction. A mortar type mixer is preferably used withfine particulate fillers. Many suitable products can be formed with anapproximately 1:1:2 ratio by volume of brine: MgO composition:aggregate, using brine, MgO, and aggregate formulations as describedherein. The precise amount of aggregate may vary greatly, however, basedon the application.

When ambient temperature is above 85 degrees Fahrenheit, it isrecommended that the mixer, transporting and/or pumping equipment, andplacing tools should be cleaned and flushed with water every two orthree hours. If the magnesium oxychloride cement compositions areallowed to dry on steel, it is difficult and time consuming to remove.When the temperature is 100 degrees Fahrenheit or more it is advisableto chill the magnesium oxychloride solution, use a canopy over themixer, and keep the aggregate in the shade. Similarly, in coldconditions it may be necessary to heat the MgCl₂ solution to ensure allthe MgCl₂ is in solution and not precipitated due to the cold, which canresult in precipitated MgCl₂.6H₂O crystals.

It has been determined that the setting reaction initially takes aboutfour hours, but additional setting can continue for up to 72 hours ormore. Because complete setting takes a number of hours, where no orlimited fillers are added, the mixed but unset cement can be applied tovarious surfaces by methods similar to painting such as by coating,dipping, brushing, spraying, and the like. The liquid mixture can alsobe arranged into a desired shape before setting as well, for example bymolding or application to a desired space or surface.

III. Applications

The inventive cement compositions can be used for a variety of purposes,from conventional use in repairing damaged concrete surfaces and coatingsubstrates with a stucco-like surface to fireproofing underlyingmaterials such as insulation, providing fire proof insulation layers, orproviding durable road striping.

For example, the inventive cement compositions can be used as a fireresistant coating on combustible materials. In one embodiment, freshlymixed MgO and MgCl₂ can be applied directly by brushing, dipping orspraying to the underlying material that is to be protected. Forexample, the freshly mixed cement can be brushed, dipped, or sprayedonto a soundproof foam or other insulation that is particularlycombustible and emits toxic chemicals upon combustion. Although thecement coating will not ultimately stop the foam from combusting ifexposed to enough heat for a long enough time, it may prevent the foamfrom rapidly catching fire from a spark and will slow the spread of fireacross the foam. Of course, a filler such as perlite and optionallyadditional fillers such as inorganic pigments can be added.

As another example, a large amount of a suitable filler, for example atleast about 50%, preferably from about 50% to about 75%, of perlite canbe admixed so that a half inch or more thick layer can be added toprovide a more persistent fire proofing layer. Such a thick layer couldhave applications in protecting steel beams in high rise construction,for example.

As another example, the cement compositions can be admixed with a lightweight filler such as expanded polystyrene beads to form a lightweightyet thick fire proof insulation. By way of example, such a filler willbe at least about 40% of the fire proof insulation cement, morepreferably from about 50% to about 75%. Such a lightweight fire prooflayer could have particular utility as a filler in fire barrier doors toinexpensively increase the fire rating of the door. In this embodiment,the cement can be either added to a door core while the cement is stillflowable or it can be molded to a suitable shape and added to the doorduring assembly.

As another example, traffic marking paints such as road stripes can beformed using the inventive cements with fillers such as silica sand andglass beads. Other reflective agents and pigments as are known in theart can also be added to provide the desired color, hue, consistency,and any other desired characteristic. An example composition includesmixed MgO and MgCl₂, silica sand, and glass in an approximately 1:1:1ratio by weight with a small amount of pigments such as titanium dioxide(white). Variations on this example and methods of applying the trafficmarking paint on streets will be apparent to those skilled in the art inview of the disclosure herein. One advantage of the inventive methodsand compositions is that the use of preferred oxide pigments does notresult in the release of harmful volatile organic gasses.

The high bond strength makes magnesium oxychloride cement compositionswithin the scope of the present invention ideally suited for concreterepair, mortar, and stucco applications. A major problem with existingconcrete repair compositions is that the bond between the compositionand the existing concrete is relatively weak. Similarly, existing stuccocompositions require stucco wire for support.

In contrast to existing stucco compositions, the stucco compositionswithin the scope of the present invention may be applied directly to thesubstrate without stucco wire or paper. Conventional wisdom teaches thatstucco wire and some moisture barrier, such as Kraft paper, existbetween the stucco composition and the substrate. The stucco wire is forsupport and the barrier is to separate the rigid stucco composition fromthe substrate. The reason why current stucco compositions are preferablyseparated from the substrate is because many stucco substrates expand,contract, or flex to one degree or another over time. Such movement ofthe substrate would cause typical stuccos to crack or fail if applieddirectly to the substrate.

It has been found that the magnesium oxychloride cement stuccocompositions within the scope of the present invention flex sufficientlyto permit them to be applied directly to substrates without fear ofsubsequent cracking. Due to this high flexibility combined with highbondability, the stucco compositions within the scope of the presentinvention do not require stucco wire or paper, unless required by localbuilding codes, but may be applied directly to the substrate surfacewhere the wall structure provides a moisture barrier, or where thestructure use does not require it. As a result, they may be appliedfaster and at a reduced cost than conventional stuccos.

Moreover, the stucco compositions within the scope of the presentinvention may be applied in a single coat as opposed to multiple coatsrequired by currently known stucco compositions. Because of the highstrength and low water absorbence of less than 5%, the stuccocompositions of the present invention may be applied with a thicknessreduced to ⅜ inch in moderate climates. Furthermore, it has been foundthat the stucco compositions within the scope of the present inventiondo not “photograph” underlying mortar joints when applied over concreteblocks.

The stucco compositions within the scope of the present invention may besprayed onto the substrate surface or troweled. Generally, to be sprayedthe stucco composition should have a lower viscosity than a troweledstucco composition. This can be achieved by reducing the amount of addedaggregate relative to the other components.

The magnesium oxychloride cement compositions within the scope of thepresent invention are also particularly adapted for casting variousornamental and functional products. For example, landscaping productsincluding precast post and panels for fencing, stepping stones, lawnedging, slope protectors, cast fountains, ornaments, splash blocks,shrub and flower pots, etc. can be produced from the cement compositionsof the present invention. A variety of other products including hollowbuilding blocks, slabs, bricks, parking lot bumpers, meter boxes, manteland hearth stones, terrazzo, burial vaults, porcelain finish castings,light weight insulating, and fireproof products, etc. may also beproduced by the cement compositions within the scope of the presentinvention.

As discussed above, the choice of aggregates determines the type ofproducts which may be produced by the cement compositions. For example,if the castable product does not require high strength or other specialcharacteristics, inexpensive aggregates may be used in connection with a“lean” cement mixture. On the other hand, if the cement product is tohave a porcelain-like finish, then higher quality aggregates andcontrolled cement compositions are important.

For large castings where semi rough or rough surfaces are acceptable,coarse aggregate up to pea gravel or ⅜ inch size will provide highstrength and low absorption. For small, delicate or intricate castings,aggregate sizes comparable to about #30 or finer would be required. Insome instances a maximum size aggregate of #50 or #70 would be requiredfor very detailed castings.

For instance, when a large vase or urn is cast and it is desired to havethe aggregate show on the surface, #8 aggregate would be used. For thistype is casting where a smooth, bubble-free surface is desired, it hasbeen found that vibrating eliminates any air bubbles which mightotherwise form on the surface. In the process, the aggregate is forcedto the outside surface against the mold and any air bubbles at thesurface are forced to the interior of the casting. The use of a vacuumchamber to de-gas can also be used.

It has been found that different sized aggregate particles containing #8and #16 silica sand included in the castable concrete composition withinthe scope of the present invention produces high quality castings ofboth functional and ornamental products. In the case of castings havinga porcelain-like finish, there is no need for firing or glazing theproduct. It has also been found that an exceptionally smooth andaccurate casting may be achieved by including smaller sized silica sand,such as #70 and #200 silica sand, into the castable concretecomposition.

The following examples further illustrate certain properties andcharacteristics of the magnesium oxychloride cement compositions withinthe scope of the present invention. These examples are intended to bepurely exemplary of the use of the invention and should not be viewed asa limitation on any claimed embodiment.

EXAMPLES 1-2

A magnesium oxychloride cement was formed by the methods disclosedelsewhere herein with an approximately 32.6° GSL brine and an 85.6% MgOcomposition with no fillers. Two panels of plywood were provided and onewas brush coated with a thin layer of the wet magnesium oxychloridecement and the cement was allowed to cure.

The two panels of plywood were place vertical and a flame from a propanetorch was applied to each panel. It was empirically observed that theuncoated panel quickly ignited and the flame spread across the panel.The coated panel, however, did not readily ignite, even under a steadyflame. Eventually, a steady flame applied to a point on the coatedplywood resulted in localized combustion, but a spreading flame did notoccur. Similarly, when the flame was applied to the top edges of thepanels, it was observed that the flame spread along the top surface ofthe uncoated panel but did not spread on the top surface of the coatedpanel.

Next, two pieces of sound proof foam were provided and one was coatedwith the wet magnesium oxychloride cement and allowed to cure. Flamefrom a propane torch was applied to each foam piece. The uncoated foampiece quickly burst into flame upon contact from the propane torch flamewhile the coated foam piece did not.

Example 3

The reaction kinetics of cement were evaluated as follows. Magnesiumchloride brine was obtained from two sources. One “pure” brine wasprepared from deionized water and analytical reagent grade MgCl₂.6H₂Ocrystals with a purity of 99.99%. An industrial “impure” Great Salt Lakebrine was also obtained. This industrial brine had the manufacturingspecifications noted hereinabove.

Magnesium oxide (MgO) was obtained came from two sources. One was anultra pure analytical reagent grade MgO with a purity of 99.999%. Theother MgO was an industrial product MgO. A scanning electron microscope(SEM) with energy dispersive x-ray analysis (EDAX) analysis of theindustrial product MgO Powder is as follows:

TABLE 4 Element Wt % Mol % MgO 84.47 89.28 SiO₂ 3.98 2.82 SO₃ 3.84 2.04CaO 7.71 5.85 Total 100 100

A series of cement samples were prepared according to Table 5 below. The“A” samples used “impure” GSL brine at 33.2±0.17% weight MgCl₂, the “B”samples used “impure” GSL brine diluted to 28.9±0.15% weight MgCl₂, the“C” Series used “pure” brine at 28.9±0.15% weight MgCl₂, and the “D”series used “impure” GSL brine diluted to 20±0.11% weight MgCl₂.

TABLE 5 Brine MgO Powder Molar Ratio Sample (% wt. MgCl₂) (lbs/galBrine) gm/L MgO:MgCl₂:H₂O A1 33.2 ± 0.17 7.5 898.74  4.96:1:10.64 A233.2 ± 0.17 8 958.65  5.29:1:10.64 A3 33.2 ± 0.17 9 1078.45 5.95:1:10.64 A4 33.2 ± 0.17 10 1198.3  6.61:1:10.64 A5 33.2 ± 0.17 111318.1  7.27:1:10.64 B1 28.9 ± 0.15 7.5 898.74  5.75:1:13 B2 28.9 ± 0.158 958.65  6.13:1:13 B3 28.9 ± 0.15 9 1078.45  6.90:1:13 B4 28.9 ± 0.1510 1198.3  7.66:1:13 B5 28.9 ± 0.15 11 1318.1  8.43:1:13 C1 28.9 ± 0.157.5 898.74  5.75:1:13 C2 28.9 ± 0.15 8 958.65  6.13:1:13 C3 28.9 ± 0.159 1078.45  6.90:1:13 C4 28.9 ± 0.15 10 1198.3  7.66:1:13 C5 28.9 ± 0.1511 1318.1  8.43:1:13 D5   20 ± 0.11 11 1318.1 13.31:1:21.14

Through a series of SEM micrographs, x-ray-spectra, and strength testson the samples, it was determined that cements made from MgO and MgCl₂brines set predominately from the 5 phase reaction. The setting time wasdetermined to be less than 4 hrs, however the setting reaction continuedfor up to 72 hours at an ever-slower rate. After 24 hours of setting,the cements have substantial strengths. Cements with ratios that arestoichiometric with the 5-phase reaction were the strongest observed.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method for forming a cementitious composition, the methodcomprising providing a first volume of a magnesium chloride (MgCl₂)brine solution, the brine solution having a specific gravity in therange from about 27° Baume to about 34° Baume; and providing a secondvolume of a magnesium oxide (MgO) composition, the second volume and thefirst volume having a weight ratio that is based upon their respectiveconcentrations and is selected to provide sufficiently stoichiometricratios of MgCl₂, MgO, and H₂O to preferably form a magnesium oxychloridecement composition according to the 5 phase reaction:5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O; and mixing the first volume withthe second volume to form the magnesium oxychloride cement composition.2. The method of claim 1, wherein ratio comprises from about 1.1:1 toabout 1.9:1 by weight.
 3. The method of claim 1, wherein ratio comprisesfrom about 1.3:1 to about 1.7:1 by weight.
 4. The method of claim 1,wherein the magnesium chloride brine solution comprises brine preparedfrom the Great Salt Lake, having one or more mineral impurities, andhaving a specific gravity of greater than about 30° Baume.
 5. The methodof claim 1, wherein: the first volume comprises at least one gallon ofmagnesium chloride brine solution having a specific gravity in the rangefrom about 28° Baume to about 34° Baume and; the second volume comprisesfrom about 7 pounds to about 8 pounds of magnesium oxide (MgO)composition for each gallon of magnesium chloride brine solution.
 6. Themethod of claim 1, wherein the magnesium oxide composition contains saltor mineral impurities other than magnesium oxide, the total amount ofthe impurities being in the range from about 5% to about 20% of themagnesium oxide cement composition.
 7. The method of claim 1, furthercomprising admixing one or more filler materials with the magnesiumoxychloride cement composition.
 8. The method of claim 7, wherein thefiller comprises a combination of different sized aggregate particles.9. The method of claim 7, further comprising using the cementitiouscomposition as mortar in construction.
 10. The method of claim 7,further comprising applying the cementitious composition as stucco. 11.The method of claim 1, further comprising applying the cementitiouscomposition to a combustible material as a fire proof insulation layerbefore the cementitious composition sets.
 12. The method of claim 11,wherein the act of applying the cementitious composition is performed byspraying, dipping, or brushing the cementitious compound to thecombustible material.
 13. The method of claim 1, wherein thecementitious composition comprises a traffic marking paint and themethod further comprises admixing a pigment with the cementitiouscompound before it sets and applying the unset cementitious compound toa paved surface.
 14. The method of claim 1, further comprising: mixingthe first volume with the second volume from about one minute to aboutseven minutes to form the magnesium oxychloride cement composition;admixing one or more filler materials with the magnesium oxychloridecement composition before the magnesium oxychloride cement compositionsets.
 15. A method for forming a cementitious composition, the methodcomprising providing a first volume of a magnesium chloride (MgCl₂)brine solution; and providing a second volume of a magnesium oxide (MgO)composition, the second volume and the first volume having a weightratio that is based upon their respective concentrations and is selectedto provide sufficiently stoichiometric ratios of MgCl₂, MgO, and H₂O topreferably form a magnesium oxychloride cement composition comprising atleast about 80% of the 5 phase compound:5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O; and providing one or more fillers.16. The method of claim 15, wherein the magnesium oxychloride cementcomposition comprises at least about 90% of the 5 phase compound. 17.The method of claim 15, wherein the magnesium oxychloride cementcomposition comprises at least about 90% of the 5 phase compound.
 18. Amethod for forming a cementitious composition, the method comprisingproviding a first volume of a magnesium chloride (MgCl₂) brine solution;and providing a second volume of a magnesium oxide (MgO) composition,the second volume and the first volume having a weight ratio that isbased upon their respective concentrations and is selected to providesufficiently stoichiometric ratios of MgCl₂, MgO, and H₂O to preferablyform a magnesium oxychloride cement composition according to the 5 phasereaction:5MgO+MgCl₂+13H₂O→5Mg(OH)₂.MgCl₂.8H₂O; and mixing the first volume withthe second volume from about one minute to about seven minutes to formthe magnesium oxychloride cement composition.
 19. The method of claim16, further comprising admixing one or more filler materials with themagnesium oxychloride cement composition subsequent to the mixing butbefore the magnesium oxychloride cement composition sets.
 20. The methodof claim 16, wherein the mixing occurs from about five minutes to aboutseven minutes.